命令 docker 启动 -a<container id> 什么都不做，“Ubuntu 20.04.02 LTS”</container>

Question

i'm trying to run the start command in docker after creating a container. for example:

$ docker create busybox echo hi there

it gives me the id of that container like 4e59d0fe8584bb4dcaf44dbce100253b6767bf51546edc27f29f39f52ed57957

and when i try to start that container without any flags like: -a flag it works, but it only gives me that id back again. but when i try to show the output using the attach -a flag, actually nothing happened, even it didn't give me an error, simply the command still running without anything happened.

i also couldn't kill the command and stop the execution by Ctrl+c, so the only option i had to close the terminal

i tried to make the problem clear as possible as i can

Answer 1

You can run the image via this command:

docker run -it busybox

It goes you to shell environment and you have -i (interactive) -t (tty) terminal, which means you see the terminal.

Answer 2

The default CMD (PID1) for busybox image is sh , see this .

For docker create busybox echo hi there , the COMMAND becomes echo hi there . This means after container starts, it will first execute echo hi there , then as PID1 exit, the container exit too. If you use docker ps , you won't find your container, you could just find your exited container with docker ps -a .

So,

• If you intend to run a one time task, then as the container finish its task, it's normal you could not enter into container anymore.

• If you intend to run a daemon task, leave the container service there, you should choose a command which won't finish after run, then your container will still there.

For your case, to quick let you understand it, you could use next to have a quick understanding, use tail -f /dev/null to let the container not exit:

# docker create busybox sh -c "echo hi there; tail -f /dev/null"
840d7c972a96712e48c9aa391aa63638fb10e12307797e338157105bdfb6934e
root@shlava:~# docker start 840d7c972a96712e48c9aa391aa63638fb10e12307797e338157105bdfb6934e
840d7c972a96712e48c9aa391aa63638fb10e12307797e338157105bdfb6934e
root@shlava:~# docker logs 0ae2d689e63a8688213d1eaf285e555ba3d672b8953f0d2730a1897c9d648a26
hi there
root@shlava:~# docker exec -it 0ae2d689e63a8688213d1eaf285e555ba3d672b8953f0d2730a1897c9d648a26 /bin/sh
/ #